ABSTRACT Pancreatic cancer (PC) will be the second leading cause of cancer-related mortalities by 2030, highlighting the importance of the development of new therapeutic modalities. One of the important reason of the PC aggressiveness is the presence of dense stroma, predominantly consisting of activated fibroblast and extracellular matrix (ECM) proteins. The deposition of the ECM proteins constricts the blood vessels leading to poor tumor perfusion, which impede the delivery of chemotherapeutics like gemcitabine, resulting in the poor therapeutic efficacy. Multiple studies have attempted to target PC stroma by modulating TGF-beta, EGFR, and hedgehog signaling and enzymatic degradation of the ECM protein in the preclinical models, but with little success. Using our novel 3D organoid system, generated from the PC and stromal cells, we investigated the impact of a novel first- in- class inhibitor of leukemia inhibitory factor receptor (LIFR), EC359 (International patent WO 2016154203 A1) on specific targeting of the activated fibroblast associated with the PC. EC359 is a novel steroidal small molecule that can readily diffused in microenvironment and specifically targets stromal cells by inhibiting leukemia inhibitory factor (LIF)-induced ECM expression and remodeling through JAK-STAT pathway. LIF is overexpressed in a subset of tumors that undergo extensive matrix remodeling, and have high stromal compartment such as PC. Our preliminary studies in autochthonous murine models have demonstrated that LIF is significantly upregulated during PC progression. Targeting LIF will offer another advantage, by depleting cancer stem cells, it will further prevent the therapeutic resistance. Based on previous findings and our preliminary studies, we hypothesize that LIFR targeting by EC359 will reduce the desmoplastic reaction in pancreatic tumor and improve the efficacy of the gemcitabine treatment. This fast track application will evaluate the in vivo efficacy of EC359 in combination with gemcitabine using state of art autochthonous murine models, patient derived xenografts (PDX), and metastatic models during Phase 1 and Phase 2 studies based on measureable milestones. In Phase I, we will evaluate the impact of EC359 and gemcitabine combination on pancreatic ductal adenocarcinoma (PDAC) tumorigenesis using orthotopic (OT) murine models. The proposed study will transition to the phase 2 after significant clinical benefit in terms of tumor regression (minimum 50%) by the combination therapy. In Phase 2, we will undertake Aim 1 to determine the therapeutic efficacy of EC359 treatment in combination with gemcitabine in autochthonous and PDX models of PDAC model. Aim 2 will determine the therapeutic efficacy of EC359 treatment in combination with gemcitabine in metastatic models of PDAC, and in Aim 3, we will proceed with process development and GMP (good manufacturing practice) synthesis of EC359 for dose ranging toxicology-studies in rodents and dogs. IMPACT: Simultaneous targeting of the pancreatic tumor stroma and stemness by EC359, attributes responsible for inherent drug resistance, will provide novel therapeutic regimen for the management PC patients. With the availability of GMP grade EC359, the findings from the proposed study will quickly lead to the clinical trials.